MH370: Curtin University team checks undersea recorders for sounds of plane crash

While the recorders offered initial promise, they have brought searchers no closer to finding the missing airliner.

AAP: Richard Wainwright, file photo

A number of undersea recorders have been carefully checked by an Australian team to see if any sounds could be linked to missing Malaysian Airlines flight MH370.

Curtin University's Centre for Marine Science and Technology maintains a number of undersea sound recorders with hydrophones around the Australian coast.

When satellite data showed the missing airliner had tracked south into the Indian Ocean, researchers at the centre asked whether the crash could have been recorded on one of their devices.

"We decided it would be worthwhile to retrieve one of those recorders that potentially could have picked up signals from the aircraft hitting the water," said Alec Duncan, a senior lecturer and research fellow at the centre.

That recorder was located off Rottnest Island near Perth, and the initial review of the data was encouraging.

"There was one, possibly two signals in that data that were reasonably consistent in terms of when they occurred with what we knew about the aircraft," he said.

But apart from a recording of the sound and the time it arrived, there was little information in the signal. There were no details of the sound's distance or direction.

To assess if it was the crash of MH370, the university team needed more data.

They turned to a different source, a set of hydrophones off Cape Leeuwin maintained as a listening station under the Comprehensive Nuclear Test Ban Treaty.

"We found a signal which was consistent with the one that we'd seen on our own recorder," Dr Duncan said.

The signal also gave them a bearing showing the direction from which the sound originated - the Indian Ocean.

The next challenge was to calculate the distance to see whether the sound's point of origin fell within the predicted flight path of the missing airliner.

Sound placed deep in Indian Ocean

By cross-checking the arrival times of the sound at the Rottnest and Cape Leeuwin recorders, the team was able to calculate a distance that placed the sound deep in the Indian Ocean.

The team reported their findings to the Australian Transport Safety Bureau.

But the calculations were complex and the margin for error significant, creating a large degree of uncertainty about the precise location of the sound.

"We can give a reasonably good bearing for that noise but we have a very large uncertainty in the range direction," Dr Duncan said.

Maybe it wasn't the impact itself. Maybe we heard something in the aircraft imploding as it sank.

Alec Duncan

Even with that uncertainty, he said the estimated range to the source places it well outside the current predicted flight path of MH370.

"Unfortunately, it now looks as though that's not consistent with the other information they have about the aircraft," Dr Duncan said.

The predicted flight path of MH370 showed an arc of travel into the southern Indian Ocean, more than 1,000 kilometres off the coast of WA, some time on the morning of March 8.

The sound recorded by Curtin University presents two conflicts with that data.

"The time of the [sound] event is a bit too late," Dr Duncan said.

"But you can explain that away by saying well, maybe it wasn't the impact itself. Maybe we heard something in the aircraft imploding as it sank."

Searchers no closer to finding missing airliner

The calculated distance to the source of the sound posed another problem.

The researcher's calculations placed it "thousands of kilometres" beyond the predicted flight path.

Dr Duncan said it was still "slightly possible" that the sound was made by the plane crashing.

"Well, I think it's only possible if there's a problem with some of the other data that they have," he said.

He said the predicted flight path calculated from the Inmarsat satellite data would have to be wrong for the sound recording to be right.

"It's quite possible that the sound signal is unrelated to the aircraft," Dr Duncan said.

"There are natural seismic processes and things like that can produce signals that are similar to the signal we detected on these receivers."

While the undersea recorders offered initial promise, they have brought searchers no closer to finding the missing airliner.

Dr Duncan said the team's current conclusion was that the sound was probably not from the crashing aircraft.

"Everybody would love this to be related to MH370 because it would give them a cross bearing [on the predicted flight path] and that would vastly reduce their search areas," Dr Duncan said.